Previous work with macrolides suggests that this class of agents may have activity against the cryptosporidiosis parasite. The aims of this study are to: (1) evaluate the safety and efficacy of ascending doses of clarithromycin; (2) compare the absorption and tolerability of the tablet and liquid forms of clarithromycin; and (3) evaluate the impact of malabsorption, as measured by d-xy-lose absorption, on the bioavailability and efficacy of clarithromycin for AIDS related cryptosporidial enteritis. Progress report and summary of findings: No new subjects were enrolled during this period. Analysis of the study is ongoing. Eight subjects were enrolled and seven completed the full seven week treatment course. Four of the eight subjects experienced a sustained reduction in bowel movement frequency of at least 30% by the end of treatment. In four subjects, stool kryptosporidium oocyst grade was consistently lower during therapy; in one subject, stool oocysts were eradicated. Some subjects receiving the liquid form of clarithromycin experienced taste disturbance, but this did not significantly affect compliance.